This invention generally relates to the detection and elimination of cardiac arrhythmia and particularly atrial fibrillation.
Atrial fibrillation is the disorganized depolarization of a patient""s atrium with little or no effective atrial contraction. This condition may be chronic or intermittent, and it presently affects approximately 2 million or more people in the United States alone. For atrial fibrillation refractory to conventional drug therapy, it has been conventional practice to make incisions in the atrial wall, to surgically segregate the tissue thereof, to discontinue the atrial fibrillation. The atrial segments formed by the surgical segregation are electrically isolated and too small to allow the fibrillation to continue. However, the surgical technique is quite traumatic and is unacceptable to a large fraction of those patient""s experiencing atrial fibrillation or flutter. Avitall in U.S. Pat. No. 5,487,385 discloses the use of high frequency electrical energy with a specific intravascular electrophysiological (EP) device to form linear ablations within a patient""s atrial chamber to provide results similar to the surgical techniques in terminating atrial fibrillation but with significantly reduced trauma. However, the Avitall device cannot be readily placed within the patient""s atrial chamber and provide the necessary contact between the electrodes on the device and the atrial tissue to generate linear lesions of a requisite length when RF electrical energy is emitted from the electrodes.
What has been needed is an ablation assembly which can be readily manipulated within a patient""s atrial chamber to generate effective linear lesions at any desired location within the atrial chamber. The present invention satisfies these and other needs.
This invention is directed to an intravascular assembly suitable for forming linear ablations within a chamber of a patient""s heart, which is particularly suitable for treating atrial fibrillation and flutter.
In a broad sense the assembly of the invention comprises a delivery member with an inner lumen extending therein, and an elongated support element in a distal section of the delivery member, and an elongated EP device disposed within the inner lumen of the delivery member and fixed by its distal end within the distal portion of the delivery member. The elongated support element is coextensive at least in part with an elongated opening in a distal section of the delivery member.
Longitudinal movement of the EP device within the inner lumen of the delivery member causes the distal portion of the EP device to arcuately extend out and away from the distal section of the delivery member. The supporting member in the distal portion of the delivery member provides support to the distal end of the EP device and ensures that the distal portion of the EP device completely engages the inner surface of the patient""s heart chamber along a length thereof for emitting high frequency (RF) electrical energy for the purpose of effective linear ablation of heart tissue within the patient""s heart chamber. Additionally, the electrode may be used for the collection of electrical signals from the surface of the atrial chamber.
Effective detection of electrical activity is necessary to accurately locate the arrythmogenic site where the linear ablation is to occur and for effective tissue ablation in a linear fashion to isolate sections of the atrial wall defining the heart chamber. The EP device of the assembly has a plurality of electrodes on the distal portion thereof which may be used for both sensing or ablating. The outer dimensions of the distal portion of the EP device are generally less than 5 Fr., preferably less than 4 Fr., in diameter.
In one presently preferred embodiment, the supporting member of the delivery member is a metallic ribbon which has an elongated flat surface which faces the elongated opening in the distal section of the delivery member . It may be made from high strength materials such as stainless steel, pseudoelastic NiTi alloys in an austenite phase. The support element is preferably manually shaped into a curved or angled condition to facilitate entry of the distal extremity of the assembly within the patient""s heart chamber, particularly the right atrium, and the proper positioning of the extended distal section of the EP device against the inner surface of the heart chamber. Additionally, an elongated deflection line may be provided in a wall of the delivery member, for deflecting the distal section of the delivery member into a curved or angled condition.
The inner radius of the extended distal section of the EP device is controlled by the length of the elongated opening in the delivery member and the distance the EP device is spaced from the support element. The effective length of the elongated opening can be controlled by the longitudinal location of the distal end of a sheath disposed about the exterior of the delivery member. As the distal end of the sheath extends distally, the effective length of the elongated opening in the distal section of the delivery member is shortened and the radius of curvature of the distal section of the EP device is correspondingly decreased.